There are four basic steps in the design procedure for Visual Soakaway Design 4.
- Carry out a site investigation to determine the soil infiltration rate.
- Establish your design variables. ie Surface area, rainfall depth, soil infiltration rate, storm duration.
- Offer an initial size for the trench soakaway by filling in the dimension boxes in the “Trench Soakaway”.
- The program will then produce a visual representation of your soakaway, either the in trench or ring form (depending on which tab you are currently in). The visual soakaway may now be moved and stretched to size and will auto-design in real time.
When reviewing your design always remember to check the Design Options window. The size of the soakaway can change drastically depending on which options are selected.
No allowance is made for the time taken for run-off to discharge to the soakaway, the required storage volume is calculated on the basis of instantaneous discharge to the soakaway.
The outflow from the soakaway is under-estimated; higher infiltration rates occur at greater depths of storage in practice than are adopted in design, and because the outflow is calculated on the basis of the rainfall duration rather than the run-off duration. The latter may be considerably longer, depending on the length of drains.